Re: [RFC PATCH 10/12] mm: add the buddy system interface

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On 2015/06/25 18:44, Xishi Qiu wrote:
On 2015/6/10 11:06, Kamezawa Hiroyuki wrote:

On 2015/06/09 19:04, Xishi Qiu wrote:
On 2015/6/9 15:12, Kamezawa Hiroyuki wrote:

On 2015/06/04 22:04, Xishi Qiu wrote:
Add the buddy system interface for address range mirroring feature.
Allocate mirrored pages in MIGRATE_MIRROR list. If there is no mirrored pages
left, use other types pages.

Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
---
    mm/page_alloc.c | 40 +++++++++++++++++++++++++++++++++++++++-
    1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d4d2066..0fb55288 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -599,6 +599,26 @@ static inline bool is_mirror_pfn(unsigned long pfn)

        return false;
    }
+
+static inline bool change_to_mirror(gfp_t gfp_flags, int high_zoneidx)
+{
+    /*
+     * Do not alloc mirrored memory below 4G, because 0-4G is
+     * all mirrored by default, and the list is always empty.
+     */
+    if (high_zoneidx < ZONE_NORMAL)
+        return false;
+
+    /* Alloc mirrored memory for only kernel */
+    if (gfp_flags & __GFP_MIRROR)
+        return true;

GFP_KERNEL itself should imply mirror, I think.


Hi Kame,

How about like this: #define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_MIRROR) ?


Hm.... it cannot cover GFP_ATOMIC at el.

I guess, mirrored memory should be allocated if !__GFP_HIGHMEM or !__GFP_MOVABLE


Hi Kame,

Can we distinguish allocations form user or kernel only by GFP flags?


Allocation from user and file caches are now *always* done with __GFP_MOVABLE.

By this, pages will be allocated from MIGRATE_MOVABLE migration type.
MOVABLE migration type means it's can
be the target for page compaction or memory-hot-remove.

Thanks,
-Kame







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